1. Field of the Invention
This invention pertains to refrigeration systems of the type which employ a volatile fluid circulated between a condenser and an evaporator by a compressor, where the compressor or its controls are expected to be exposed to low winter ambient temperatures. The invention relates further to pressure controls for these systems intended to sense either refrigerant vapor pressure or oil pressure and open or close switches in response thereto.
Bellows-type pressure controls which are applied to refrigeration systems which use reciprocating compressors require a restricting element between the bellows and the point at which pressure is sensed for the purpose of smoothing the pressure pulsations generated by the compressor. These pulsations, if applied to the bellows without damping, would cause early bellows fatigue and failure. When pressure sensing elements of this sort are applied in low outdoor ambients, as in connection with refrigeration condensng units located outdoors under low temperature conditions, oil, which is circulated with the refrigerant, gets trapped in the restrictive element; either unavoidably, as in controls which measure and react to oil pressure; or inadvertently as in controls which measure suction vapor pressure. The congealed oil becomes an effective barrier to the flow of sufficient fluid to communicate the desired pressure from the system to the bellows and the control becomes inoperative.
2. Prior Art
To date I am not aware of any structure which has been constructed or arranged or intended for the purpose of deliberately providing a warmer-than-normal environment around a pressure control and its associated restricting element for the purpose of enabling the switch to operate correctly at low outdoor ambients.